1. Field of the Invention
The present invention relates to a sheet feeding equipment of image forming apparatus.
2. Description of the Related Art
Heretofore, as shown in FIG. 1, an image forming apparatus is provided with a sheet feeding cassette 1 which has a cassette plate 12 for placing a sheet 101 thereon and in which an opening 9 is provided on a part of a side plate and a bottom plate 30; with a pick up roller 10 for feeding the sheet 101 from the sheet feeding cassette 1; with a lift plate 2 for lifting the cassette plate 12 on which the sheet 101 has been placed to abut the sheet 101 against the pick up roller 10; with a lift shaft 3 to which one end of the lift plate 2 is fixed by a machine screw and the like; with a lift gear 4 fixed to an end of the lift shaft 3; with an idle gear 13 engaging with a gear section 14 of the lift gear 4; and with drive means 6 formed by a motor 22 and gear means 5 for pivoting the lift gear 4, the lift shaft 3 and lift plate 2, through the idle gear 13.
Now, when an image forming apparatus attempts to feed the sheet 101 for copying, in order to abut the sheet 101 placed on the cassette plate 12 against the pick up roller 10, the motor 22 rotates to cause the lift gear 4 through the gear means 5 and the idle gear 13 to be driven to the lower side on the view, the lift shaft 13 to be rotated, and the lift plate 2 fixed to the shaft 3 to be pivoted to the upper side. Hereby, as shown in FIG. 1, the lift plate 2 passes through an opening 9 of the sheet feeding cassette 1, whereby a tip 31 thereof abuts the cassette plate 12 and lifts the cassette plate 12 together with the sheet 101, and when the sheet 101 reaches a position at which the sheet abuts the pick up roller 10, the plate 2 stops pivoting.
When the sheet 101 abuts the pick up roller 10, the pick up roller 10 can feed the sheet 101 to the a sheet feeding roller 23, whereby the feeding of the sheet 101 is performed.
Now, if the sheet feeding cassette 1 is pulled out accidentally during the feeding of the sheet 101 by the pick up roller 10, as shown in FIG. 2, an edge of the opening 9 of the sheet feeding cassette 1 hits an edge 21 of the lift plate 2 having been lifted, to cause the sheet feeding cassette 1 or the lift plate 2 to be damaged. Therefore, heretofore, a lock device has been provided to prevent a trouble due to the pulling out of the sheet feeding cassette 1 during sheet feeding.
However, a sheet feeding equipment provided with such lock device has problems that where the lift plate is positioned at a sheet feeding position, the sheet feeding cassette cannot be pulled out, and that the equipment is complex and expensive.